1. Field of the Invention
The present invention relates to an endoscope system and to an observation method using the same.
This application is based on Japanese Patent Application No. 2006-051915, the content of which is incorporated herein by reference.
2. Description of Related Art
In endoscopy, observation of fluorescence images can give different information about a living organism from reflection images, and it is therefore beneficial in the diagnosis and observation of diseases.
For example, if a fluorescent probe that reacts with a substance originating in a diseased area to change from a non-fluorescent substance to a fluorescent substance is administered, it is possible to observe the concentration distribution of the substance originating from the disease by examining the fluorescence image.
By observing autofluorescence, that is, fluorescence originating in the living organism itself, it is possible to observe changes in the living organism and to monitor the disease.
At the same time, useful information different from that in fluorescence images is also contained in reflection images.
That is, using a reflection image, it is possible to observe the density of blood vessels, accumulation, and so forth, which allows information related to a disease, such as inflammation, to be obtained.
There are known fluorescent dyes for in vivo visualization of disease sites such as tumors and cancer tissue with high sensitivity; they act as fluorescent probes which bind with substances originating in diseased areas and emit fluorescence. A method using 5-aminolevulinic acid, which is exogenous substance, has already been employed in clinical applications (for example, see Kennedy, J. C. et al.: J Photochem Photobiol B 6:143, 1990).
However, oral administration or administration by intravenous injection or the like, as typified by the method using 5-aminolevulinic acid, requires a large amount of the agent, and therefore has the drawback that it consumes a large amount of fluorescent material, which is generally expensive.
In addition, since it is administered to the whole body, it takes time to accumulate in the tumor site. For example, because there is a time delay for accumulation at various sites in the digestive system, there is a problem in that it is not possible to observe it at the desired instant.
Furthermore, because the intensity of the fluorescence is very weak, there is a problem in that the quality of the fluorescence image tends to deteriorate due to noise and so forth.